6.  The applicant was born in 1974. He is currently detained in a cantonal prison in Regensdorf in Switzerland.
7.  On 15 October 2001, shortly after midnight, N.B. was killed by a gunshot in the back of his neck in front of the post-office in Zurich‑Schwamendingen. The applicant was suspected of having carried out the shooting.
8.  On 8 July and 21 August 2002, the prosecution authority of the canton of Zurich interrogated X as a witness. X declared that he had been at the crime scene and that he had been able to see, from a distance of twenty metres, that the applicant had shot the victim in the back of his neck. During the interrogations, the witness, the investigating judge, a police officer and a translator were sitting in a separate room, while the applicant, the former co‑accused Z. L., their respective defence counsel and two police guards were sitting in another room. The interrogation was transmitted via a sound link, and the witness’ voice was distorted in order to protect the witness’ anonymity. Following the interrogation, the defence counsel were given the opportunity to put additional questions via the sound link.
9.  At the beginning of each interrogation the applicant’s counsel declared that the modalities of the witness interrogations did not allow for an adequate exercise of the rights of the defence.
10.  On 29 January 2004, X was interrogated before the Jury Court of the canton of Zurich (Geschworenengericht). While the judges, the jury and an interpreter were sitting directly together with the witness in the hearing room, the applicant, his counsel, the interpreter, the civil parties, the public prosecutor and the journalists were placed in one of the court’s deliberation rooms. The interrogation was transmitted via a sound link and the witness’ voice was distorted in order to prevent his being identified.
11.  The applicant and his counsel were allowed to put additional questions to X. The latter, however, refused to answer a number of questions which the defence counsel considered to be important, notably the following:
“Why had X arranged a meeting with N.B.? How did X react after the crime? Did X approach the body? Did he wait for the police? Did he consume drugs? Was he afraid of someone close to the applicant? Had he been concretely threatened by someone? Did X have an argument with the applicant or with Z.L.? Where did X go after the crime? Was he on foot or did he have a vehicle? Did he have a criminal record? Was he residing legally in Switzerland? Did he wear spectacles?”
12.  On 6 February 2004, the jury court convicted the applicant of manslaughter (vorsätzliche Tötung) and of several counts of drug-trafficking and sentenced him to fourteen years and nine months’ detention. The court considered that the testimony given by X was credible and pertinent. It further considered that the conditions to allow the witness’ anonymity were met. It noted that X had submitted in a credible and convincing way that his life was in danger in case he testified, as persons close to the applicant and to Z. L. were ready to take revenge and did not even hesitate to kill somebody. According to X’s submissions, he was the only person who had observed the crime and who dared to testify. It thus appeared comprehensible that X feared reprisals. It was further obvious that the applicant had a motive to take revenge on the witness who had contributed to his conviction and to prevent him from making further testimonies.
13.  The fears expressed by X were in line with the overall picture conveyed by the other witnesses, who showed fear which was sometimes even bordering to panic when it came to making any concrete incriminating statements. The court considered that there were concrete indications that the applicant lived in an extremely violent environment in which recourse to violence and even to arms was frequent even for seemingly minor reasons. Moreover, there were specific indications that persons who had been ready to testify before the jury court had been exposed to death threats.
14.  The court further considered that the measures taken were both necessary and sufficient to prevent identification of the witness X. The court had taken a number of measures to compensate the restrictions imposed on the rights of the defence. Firstly, the witness had not been examined by the regional prosecutor (Bezirksanwalt), but by the president of the court. Secondly, the identity of X had been confirmed by the police-officer in charge of the investigation and had been known to the regional prosecutor and to the president of the court.
15.  Thirdly, the police officer and the regional prosecutor gave testimony about X’s reputation and credibility. It had thus been known that X had no criminal record and that there was no indication that he had any contact with the drug trafficking scene. There was further no indication that X had been in any way involved in the crime. It was further known that X spoke the Serbo-Croatian language. Conversely, the regional prosecutor refused to divulge any detailed information on X’s private and professional background, his education, his family situation and his residence status. The jury court considered, however, that this information was of minor importance for the assessment of credibility and that the information available gave the court a sound basis for assessing the general credibility of the witness.
16.  The court further noted that X had been interrogated in front of the complete court and that all persons participating in the decision-making process could gain a personal impression of the witness and of his reaction to the questions put to him. Furthermore, the court had taken into account that, under the case-law of the European Court of Human Rights, a conviction could not be exclusively based on testimony given by an anonymous witness. The principle of a public hearing had been safeguarded by allowing the press directly to follow the interrogation from the separate room in which the defence was seated. The court considered that the core rights of the defence had been safeguarded and that the measures taken had been proportionate.
17.  Referring to the Court’s case-law, the jury court considered that a criminal conviction must not be exclusively based on testimony given by an anonymous witness. Accordingly, the court considered that it could not rely on the anonymous witness’ testimony insofar as this constituted the only evidence available. The jury court resumed its examination by laying out general principles for the assessment of the credibility of evidence by witnesses. It considered that the applicant’s own submissions, according to which he could not have been present at the crime scene as he first entered Swiss territory in January 2002 – and thus after the victim had been killed – were contradictory and thus lacked credibility. Conversely, the court considered the testimony given by the anonymous witness, who submitted that he had seen the applicant shooting the victim, to be credible.
18.  The jury court further considered that there had been other evidence linking the applicant to the crime. There was, in particular, witness and circumstantial evidence allowing the conclusion that the applicant had been residing in the Zurich region since August 2001, that he had known the victim and that he had engaged in drug trafficking with him. As regarded the shooting of the victim, the court considered that the statements made by the witness Z. L., who had declared in a credible and convincing way to the police that the applicant had explained to him some days after the incident that he had killed N.B. before the latter could kill him, weighed heavily against the applicant, notwithstanding the fact that Z. L. did not repeat these allegations during the court proceedings, but stated that he could not remember what had happened. The testimony given by Z. L. during the police investigation was supported by the convincing submissions made by the anonymous witness, and by testimony given by a witness who had presumably met the applicant immediately after the crime. Relying on all available evidence, the jury court concluded that there was no doubt that N. B. had been shot by the applicant. With regard to the concrete factual circumstances, the jury court considered that the prosecution based its submissions mainly on testimony given by the anonymous witness. It followed that, for formal reasons, these circumstances could not be taken into account and that it had to be assumed in the applicant’s favour that the concrete circumstances had not been proven. It followed that there was no sufficient factual basis which would allow the conclusion that the applicant acted with a particular degree of scrupulousness (besonders skrupellos) which would lead to the crime being characterised as murder.
19.  The applicant lodged a nullity appeal (Nichtigkeitsbeschwerde) with the Court of Cassation (Kassationsgericht) of the canton of Zurich.
20.  By decision of 19 December 2005 the Court of Cassation quashed the judgment and remitted the case to the lower court. That court noted that the anonymous witness had been heard in camera and that the applicant’s counsel did not have the possibility directly to question the witness. Neither the applicant nor his counsel had ever seen the witness, whose personal details remained secret. The court further noted that the witness refused to answer a number of questions which the defence considered important (see paragraph 11, above). The court did not call into question that the legal conditions for granting anonymity were fulfilled in the instant case and confirmed the first instance court’s finding that it had been necessary to protect X against possible reprisals.
21.  With regard to the applicant’s rights under Article 6 of the Convention, the court considered that the maintenance of the anonymity of the witness X and the fact that X had been shielded from sight and that his voice had been distorted seriously interfered with the defence’s right to confront the witness. The fact that the prosecution and the presiding judge were aware of the witness’ identity could not be regarded as a counterbalancing factor as such. Given the fact that all judges were accountable for the judgment, and that it was the role of the defence to examine the findings of the prosecution from the defendant’s point of view, it appeared problematic that the presiding judge had knowledge that was superior to that of the other members of the court, including the jury, and that the latter had more knowledge than the defence. Adequate compensation could only be conceivable if at least the defence had the right directly to take part in the interrogation of the witness and was given the opportunity to assess the witness’ credibility; however, this possibility was not granted in the instant case.
22.  Relying on the Court’s case-law (the court referred to the cases of Doorson v. the Netherlands, 26 March 1996, Reports of Judgments and Decisions 1996‑II and Van Mechelen and Others v. the Netherlands, 23 April 1997, Reports of Judgments and Decisions 1997‑III), the court considered that the criminal court could not rely on the testimony given by the anonymous witness for two separate reasons: Firstly, according to the case-law of the Court, it was decisive whether the applicant’s defence counsel had been present during the interrogation of the anonymous witness or had at least been in a position to follow the interrogation via an audio‑visual link and to put questions. As this had not been the case, the modalities of the witness’ interrogation did not comply with the standards set up by the Court and were thus contrary to Article 6 § 3 (d) of the Convention.
23.  Secondly, the court examined whether the testimony given by the anonymous witness had to be regarded as being “decisive” for the applicant’s conviction within the meaning of the “sole or decisive” rule developed by the Court. It noted that the anonymous witness was the only direct witness of the crime at issue, as the remaining witnesses only gave evidence by hearsay. It was thus obvious that the anonymous witness’ testimony had more than only minor relevance for the assessment of the evidence. Even though the evidence given by other – indirect – witnesses carried a certain weight, the anonymous witness had to be regarded as the decisive evidence (“massgebliches Beweismittel”), and was decisive to an extent which, under the Court’s case-law, excluded the possibility of having recourse to this evidence in order to establish the applicant’s guilt.
24.  On 3 February 2006 the senior public prosecutor (Oberstaatsanwalt) of the canton of Zurich lodged a nullity appeal against the decision of the Court of Cassation.
25.  By judgment of 2 November 2006 the Federal Tribunal (Kassationshof) quashed the decision of 19 December 2005 and remitted the case to the Court of Cassation. That court considered that the lower court’s judgment did not comply with the principle of free appreciation of the evidence under Article 249 of the Federal Law on Criminal Procedure (Grundsatz der freien Beweiswürdigung, see relevant domestic law, below).
26.  The Federal Tribunal confirmed that it had been necessary to protect the witness by shielding his appearance both from the applicant and from the applicant’s counsel. It considered that the counsel was not under any legal obligation to transmit information on the witness’ identity to the applicant. Even if such a duty existed, the risk that the defence counsel did not respect this obligation or inadvertently divulged information to his client was unacceptably high. The tribunal further considered that it was compatible with Article 6 of the Convention to consider the testimony given by an anonymous witness insofar as it could complete – like a mosaic stone – the picture gained through other evidence, which was in itself not sufficient to support an establishment of guilt, but established a strong suspicion, and thus contributed to a full establishment of guilt.
27.  The tribunal further reviewed the other evidence examined by the jury court and concluded that this evidence, taken separately, would have been sufficient “to establish a strong suspicion of a criminal offence, or even to establish his guilt”. The tribunal reiterated that the jury court had considered that the testimony given by the witness X had been credible and that it was, furthermore, in line with the scientific conclusion that the victim had been killed by gunshot in the back of his neck on 15 October 2001.
28.  The tribunal concluded that the anonymous testimony only served as one piece of a mosaic which enforced the conclusion drawn from the remaining evidence. It followed that the criminal courts were not prevented from taking this evidence into account.
29.  On 12 February 2007 the Court of Cassation rejected the applicant’s nullity appeal. On 19 April 2007 the Federal Tribunal rejected the applicant’s appeal.